Reminds me of the days when you could look up public camera feeds with a specific string in a google search. Some of the camera pages had controls! Spent a day with friends in a college dorm scrolling through them.
Symplectic integrators are the approach I used for some old galaxy simulations. Page 5 on the attached paper was my main reference, eq 22
https://arxiv.org/pdf/cond-mat/0110585
I believe this is used in several academic codes for long term N-body calculations.
Is it possible your wireless channel was overused? Most of my neighbors have comcast, as do we. I've had poor coverage and connection also, couldnt even get our wireless printer to work anymore. I used a program called WifiInfoView and viewed how many nearby wireless networks there were, their signal strengths, and set my router to a channel that wasn't being used.
Cleared up all of our problems instantly. I would check this, perhaps his google modem was preset to another channel.
It's not painful, but feels like pop rocks in my ear canal.